Power generation plant and power generation method without emission of carbon dioxide

ABSTRACT

In a closed type thermal power generation plant, the fuel is supplied in the combustor and burnt therein in the presence of oxygen, instead of air. The combustion gas mainly including water and carbon dioxide is delivered from the combustor into the turbine. A turbine exhaust gas is fed into the waste heat boiler to carry out heat exchanging operation therein and an exhaust gas mainly including water component and carbon dioxide from the waste heat boiler is fed into the condenser. The gas component mainly including the carbon dioxide is separated from the condensate in the water-gas separator and may be fed into the combustor in a compressed state, or the separated gas component may be recovered externally to the plant without emitting the same into the atmosphere. The separated condensate is fed into the waste heat boiler to be subjected to heat exchanging operation therein to generate superheated steam which is to be fed into the combustor, or may be recovered externally. 
     Further, a steam turbine may be connected to the waste heat boiler and generator. A condensor may then be connected to the steam turbine and waste heat boiler so that the steam turbine, condenser and waste heat boiler constitute a closed cycle.

This is a division of application Ser. No. 07/426,206, filed on Oct. 25,1989, now U.S. Pat. No. 4,175,945.

BACKGROUND OF THE INVENTION

This invention relates to a power generation plant and a powergeneration method without emission of carbon dioxide and, moreparticularly, a thermal power generation plant and method of a closedcycle type incorporating a carbon dioxide recovery system.

In a conventional power generation plant, particularly a thermal powergeneration plant, a steam turbine or gas turbine, or the both are drivenby combustion gas energy generated by burning fuel with air in acombustor and the air is also utilized as a working fluid gas compressedin a compressor. In such a thermal power generation plant, natural gas,petroleum fuel gas or coal gas has been utilized for the fuel gas, whichgenerally includes carbon components such as carbon (C), carbonmonooxide (CO), or other hydrocarbon (CmHn). Accordingly, the combustiongas after the burning of the fuel in the presence of air includes carbondioxide (CO₂), nitrogen oxide (NO_(x)) and sulpher oxide (SO_(x))generated by the oxidation of sulfur contained in the fuel in additionto nitrogen gas (N₂) and oxygen gas (O₂) contained in the air.

The exhaust of the harmful gas such as NO_(x), SO_(x) and CO₂ in theatmosphere provides a significant problem for an environmentalpollution. It is not easy to restrict the generation of NO_(x) in thecombustion gas as far as the fuel gas is burnt in the presence of air inthe combustor and, in order to remove the NO_(x) and SO_(x), in theconventional power plant, additional equipment is incorporated for theremoval thereof in the process of gassification and the following gasrefining process. In the meantime, in order to remove the CO₂ containedin the gas to be exhausted in the atmosphere after the combustion, it isnecessary to remove and recover the CO₂ from the exhaust gas before theemission in the atmosphere.

In order to recover the CO₂ in the exhaust gas, in the conventionalpractical method, the CO₂ is separated and removed by utilizing asolvent having a property capable of selectively absorbing the CO₂ fromthe exhaust gas at a low temperature. The solvent including highlyconcentrated CO₂ also has a property capable of discharging the CO₂ byheating the same, whereby the CO₂ can be recovered by heating thesolvent including the highly concentrated CO₂.

However, the method of recovering the CO₂ by utilizing the solventprovides the following problems.

First, the CO₂ is recovered in contact of the exhaust gas in thesolvent, but the contacting time is limited; that is, it is impossibleto infinitely contact the exhaust gas to the solvent during theoperation of the thermal power plant and, accordingly, some amount ofthe CO₂ remains unrecovered in the exhaust gas. Second, an extremelyvoluminous CO₂ is usually generated in the thermal power plant, so thatthe voluminous solvent is also required as well as the heat energy forheating the solvent, which results in the increasing of the cost for theconstruction of a CO₂ recovery system and of the operation cost thereof.

In the other point of view, in the conventional thermal power plant, theair including about 80% of N₂ is utilized for burning the fuel and theexhaust gas includes a voluminous highly concentrated N₂ gas, so thatthe total amount of the exhaust gas increases and a large amount of thesolvent for recovering the CO₂ is required as described above.

SUMMARY OF THE INVENTION

An object of this invention is to substantially eliminate defects ordrawbacks encountered to the prior art as described above and to providean improved power generation plant of closed cycle type incorporating aCO₂ recovery system capable of emitting substantially no NO_(x), SO_(x)and CO₂.

Another object of this invention is to provide a closed dual fluid gasturbine power generation plant in which superheated steam and CO₂ areutilized as working fluids for the turbine operation and in which CO₂ issubstantially not exhausted externally.

A further object of this invention is to provide a closed combined cycletype power generation plant in which CO₂ is recycled and utilized as aworking fluid for the turbine operation without emitting the same in theatmosphere.

A still further object of this invention is to provide a closed H₂ O gasturbine power generation plant in which H₂ O is utilized as a workingfluid for the turbine operation without emitting the CO₂ in theatmosphere.

These and other objects can be achieved according to this invention, inone aspect, by providing a thermal power generation plant of a closeddual fluid gas turbine power generation structure comprising, acombustor in which a fuel is burnt in the presence of an oxygen, a fuelsupply means connected to the combustor to supply a fuel therein, anoxygen supply means connected to the combustor to supply an oxygentherein, a turbine operatively connected to the combustor to be drivenby combustion gas from said combustor, said turbine exhausting a turbineexhaust gas mainly composed of carbon dioxide and water component, agenerator connected to the turbine, a waste heat boiler connected to theturbine, a condenser connected to the waste heat boiler for condensingthe water gas component in a cooled exhaust gas from the waste heatboiler, a water-gas separator connected to the condenser for separatingcondensate and gas component mainly composed of carbon dioxide, thewater-gas separator being connected to the waste heat boiler to feed thecondensate thereto, the waste heat boiler being connected to thecombustor for supplying superheated steam generated in the waste heatboiler due to heat exchanging operation between the condensate and theturbine exhaust gas, and a compressor connected to the water-gasseparator for compressing the gas component mainly composed of thecarbon dioxide, the compressor being connected to the combustor forsupplying compressed carbon dioxide.

In another aspect of this invention, there is provided a thermal powergeneration plant of a closed combined cycle structure in which, insteadof the connection of the water-gas separator to the waste heat boiler asdescribed above with respect to the first aspect of this invention, asteam turbine connected to the generator is further installed in theplant and the steam turbine is connected to the waste heat boilerthrough a condenser so as to constitute another combined closed cycle.

In a further aspect of this invention, there is provided a thermal powergeneration plant, in which the compressor in the first aspect of thisinvention is removed and the gas component mainly including the carbondioxide separated in the water-gas separator is removed therefromexternally to the plant.

According to this invention, the fuel is supplied in the combustor andburnt therein in the presence of oxygen, .instead of air, the combustiongas mainly including water component and carbon dioxide is deliveredfrom the combustor into the turbine. The generator is driven by thedriving of the turbine with the combustion gas as a turbine workingfluid. A turbine exhaust gas is fed into the waste heat boiler to carryout heat exchanging operation therein and an exhaust gas mainlyincluding water component and carbon dioxide from the waste heat boileris fed in the condenser. On the way of this process, an SO_(x) removingmeans may be incorporated in a line connecting the waste heat boiler andthe condenser to remove the SO_(x). The gas component mainly includingthe carbon dioxide is separated from the condensate in the water-gasseparator and recovered without emitting the same in the atmosphere.

The separated gas component mainly including the carbon dioxide may befed into the combustor in a compressed state. The separated gascomponent may be recovered externally to the plant without emitting thesame in the atmosphere.

The separated condensate is fed into the waste heat boiler to besubjected to heat exchanging operation therein and generate asuperheated steam which is to be fed into the combustor. The separatedcondensate may be recovered externally to the plant.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a block diagram showing a layout of the first embodiment of athermal power generation plant of closed dual fluid gas turbine typeaccording to this invention;

FIG. 2 is a block diagram showing a layout of the second embodiment of athermal power generation plant of closed dual fluid regenerative gasturbine type according to this invention;

FIG. 3 is a block diagram showing a layout of the third embodiment of athermal power generation plant of closed combined cycle gas turbine typeaccording to this invention; and

FIG. 4 is a block diagram showing a layout of the fourth embodiment of athermal power generation plant of closed H₂ O gas turbine type accordingto this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a block diagram representing the first embodiment of a thermalpower plant according to this invention. The thermal power plantgenerally comprises a combustor 1, a turbine 2, a generator 3, a wasteheat boiler 4, a compressor 5, a condenser 6 and a water-gas separator7, which are operatively connected through duct means respectively tothereby constitute a closed cycle power generation plant.

Referring to FIG. 1, in detail, in the combustor 1, fuel such as coalgas fed from a fuel gas supply means F is burnt in the presence ofoxygen fed from an oxygen supply means 0. The combustor 1 is connectedto the turbine 2 through a duct 8 and the turbine 2 which is driven bycombustion gas from the combustor 1 is connected to the generator 3through a driving shaft 9. The turbine 2 is also connected to the wasteheat boiler 4 to feed exhaust gas after operating the turbine 2 througha duct 10 and the waste heat boiler 4 is connected to the condenser 6through a duct 11 to feed the exhaust gas therein. The water-gasseparator 7 is connected to the condenser 6 to separate fluid from thecondenser 6 into gas and condensate. The water-gas separator 7 isconnected to the compressor 5 through a duct 12 and the compressor 5 isalso connected to the combustor 1 through a duct 10 and to the turbine 2through a shaft 17. As described above, the power generation plant shownin FIG. 1 constitutes a closed cycle. The water-gas separator 7 is alsoconnected to the waste heat boiler 4 through a duct 13 on the way ofwhich is incorporated a feed water pump 14 to feed the condensate intothe waste heat boiler 4 and an excessive carbon oxide removing deviceincluding a suction pump P and a reservoir R is operatively connected onthe way of the duct 12 connecting the water- gas separator 7 and thecompressor 5.

SO_(x) generated by the oxidation of sulfur which may be contained inthe fuel will be preferably removed by incorporating an SO_(x) removingmeans, for example a known wet washing type, in the line 11 connectingthe waste heat boiler 4 and the condenser 6.

A known oxygen producing means may be utilized as the oxygen supplymeans for this embodiment, which may produce oxygen from air, withoutspecific technology.

The function of this embodiment will be described hereunder.

The fuel such as coal gas is introduced into the combustor 1 and burnttherein in the presence of the oxygen instead of air. In such combustionprocess, both the compressed carbon dioxide (CO₂) and superheated steamare utilized as working fluids and the CO₂ further acts to suppress theexcessive burning in the combustor 1. The constituent gases of thecombustion gas become CO₂ and H₂ O, since the principal composition ofthe fuel gas are generally C, CO, H₂, CO₂, and C_(m) H_(n) and whichreact as follows.

    C+O.sub.2 →CO.sub.2                                 (1)

    CO+1/2 O.sub.2 →CO.sub.2                            (2)

    H.sub.2 +1/2 O.sub.2 →H.sub.2 O                     (3)

    C.sub.m H.sub.m +(m+n/4)O.sub.2 →mCO.sub.2 +n/2 H.sub.2 O (4)

As shown in these equations, the combustion gas substantially includesCO₂ and H₂ O and, accordingly, an exhaust gas after the combustion gashas been utilized for driving the turbine 2 and an exhaust gas after theturbine exhaust gas has been further utilized in the waste heat boiler 4substantially include CO₂ and H₂ O. The driving of the turbine 2 istransmitted to the generator 3 through the driving shaft 9 to generatepower. The highly heated exhaust gas from the turbine 2 is fed to thewaste heat boiler 4 and utilized for heating the condensate due toso-called a heat exchanging operation and the heated condensate, i.e. H₂O, is fed into the combustor 1 in form of a superheated steam. Thecooled exhaust gas from the waste heat boiler 4 including mainly CO₂ andH₂ O is thereafter fed to the condenser 6 in which the H₂ O component inthe exhaust gas is condensed into condensate. In a case where the sulfurcomponent is contained in the fuel, the generated SO_(x) is removed bythe SO_(x) removing means S incorporated in the duct 11. The condensateand the remaining gas component, generally composed of CO_(x), are fedinto the water separator 7 in which the condensate, i.e. water isseparated from the gas component. The water is fed into the waste heatboiler 4 through the duct 13 and the gas component is fed into thecompressor 5 through the duct 12. The CO₂ fed into the compressor iscompressed therein and then fed into the combustor as working fluid forthe turbine 2. Although the most part of the CO₂ from the water-gasseparator 7 is utilized for this purpose, the excessive CO₂ generated bythe combustion of the fuel will be removed through the removing meansincluding the suction pump P and the reservoir R incorporated on the wayof the duct 12.

Further in detail, The combustion gas of high temperature is first usedto generate electric power by driving the turbine 2. The exhaust gaswhich has still a considerable heat energy is then utilized to producethe superheated steam in the waste heat boiler 4 to increase poweroutput as well as to improve the power generation efficiency. Thelow-temperature gas from the waste heat boiler 4 is thereafter led intothe condenser 6, where the water component included in the exhaust gasis substantially completely condensed into water, which is then fed tothe waste heat boiler 4 as the feed water.

The principal component of the condenser outlet gas includes CO₂, thougha small quantity of oxygen and nitrogen is included. Oxygen gasinclusion is caused by injecting excess oxygen into the combustor forrealizing complete combustion of the fuel gas and nitrogen gas inclusionis caused by the fact that in general an extremely small quantity ofnitrogen gas, which may be neglected, is included in a fuel gas such ascoal gas, even if coal is gasified in the presence of the oxygen insteadof the air. The gas component from the water separator 7 is recycled asthe main working fluid of the gas turbine. The excessive CO₂ isrecovered by the additional recovery means, so that no CO₂ is emittedfrom the power plant according to this embodiment shown in FIG. 1.

As described above, according to the thermal power plant, so called aclosed dual fluid gas turbine power generating plant, of thisembodiment, the fuel gas is burnt in the combustor in the presence ofthe oxygen, instead of the air generally including nitrogen, oxygen orother components, so that substantially no NO_(x) is contained in theexhaust gas and merely contain H₂ O which is utilized as the feed waterof the waste heat boiler for producing the superheated steam acting asworking fluid and CO₂ which is effectively utilized and recycled as theworking gas in the power plant. The excessive CO₂ generated by, theburning of the fuel is recovered without emitting the CO₂ intoatmosphere.

Accordingly, the environmental pollution can be substantially eliminatedwithout being equipped with specific means for removing harmful gas suchas NO_(x) and CO₂.

A simulation model has been constructed to estimate variouscharacteristics of the power generation plant according to thisinvention. In this simulation model, the variables and parameters whichcan be designed in realizing the power generation plant are assumed tobe the exogenous variables and parameters, respectively. The detailedexplanation of the constructed model is omitted here.

Consequently, it may be ascertained from the simulation results that wecan construct a power generation plant without emission of the CO₂ intothe atmosphere with the power generating efficiency of 43.7%. Althoughthe proposed power generation plant may require the incorporation of theextra equipments for producing oxygen and for liquefying the recoveredCO₂, this incorporation is not significant in view of the environmentalpollution due to the emission of harmful gases such as NO_(x) and CO₂and of the future utilization of the plant.

FIG. 2 is a block diagram representing the second embodiment of thethermal power plant according to this invention, which may be called aclosed dual fluid regenerative gas turbine power generating plantbecause of the construction described hereunder.

The thermal power plant represented by FIG. 2 is basically differentfrom that of the first embodiment shown in FIG. 1 in the incorporationof a regenerator designated by reference numeral 20 and the otherconstructional units or devices are substantially equal to those shownin FIG. 1. Accordingly, the detailed description of the other units ordevices are now eliminated by applying the same reference numerals asthose described in FIG. 1.

The regenerator 20 is of one kind of a heat exchanger carrying out theheat exchanging operation between the exhaust gas passing the duct 10connecting the turbine 2 and the waste heat boiler 4 and the compressedcarbon oxide passing a duct 21 connecting the CO₂ compressor 5 and thecombustor 1.

The regenerator 20 operates to recover heat energy from the turbineexhaust gas and the heat energy recovered is utilized to raise thetemperature of the main working fluid, i.e. CO₂, in this embodiment,from the compressor 5. The incorporation of the regenerator 20 makes itpossible to noticiably improve thermal efficiency of the thermal powergenerating plant.

According to the location of the regenerator 20, the CO₂ gas from thecompressor 5 is heated by the exhaust gas from the turbine 2 in theregenerator 20 due to the heat exchanging operation therebetween and thehighly heated CO₂ is then fed into the combustor 1 as the main workingfluid. The exhaust gas passing through the regenerator 20 is fed intothe waste heat boiler through the duct 22.

As described above, according to the thermal power plant shown in FIG.2, so called a closed dual fluid regenerative gas turbine powergenerating plant, of this embodiment, the fuel gas is burnt in thecombustor in the presence of the oxygen, instead of the air generallyincluding nitrogen, oxygen or other components, so that substantially noNO_(x) is contained in the exhaust gas and merely contain H₂ which isutilized as the feed water of the waste heat boiler for producing thesuperheated steam acting as the working fluid and CO₂ which iseffectively utilized and recycled as the working fluid in the powerplant. The CO₂ from the compressor 5 the, regenerator 20 due to the heatexchanging operation thereof. The excessive CO₂ generated by thecombustion of the fuel is recovered without emitting into atmosphere.

SO_(x) generated by the oxidation of sulfur which may be contained inthe fuel will be preferably removed by incorporating an SO_(x) removingmeans, for example a known wet washing type, in the line 11 connectingthe waste heat boiler 4 and the condenser 6.

Accordingly, the environmental pollution can be substantially eliminatedwithout being equipped with specific means for removing harmful gas suchas NO_(x), SO_(x) and CO₂.

In another aspect of this invention, the principle of the powergeneration plant of the character shown in FIG. 1 or 2 will bepositively adopted to a combined cycle power generation plant.

FIG. 3 shows a block diagram of the third embodiment of a thermal powergeneration plant of the combined cycle type according to this invention.

Referring to FIG. 3, in the combustor 1, fuel such as coal gas is burntin the presence of oxygen. The combustor 1 is connected to the turbine 2through a duct 8 and the turbine 2 which is driven by combustion gasfrom the combustor 1 is connected to the generator 3 through a drivingshaft 9. The turbine 2 is also connected to the waste heat boiler 4 tofeed exhaust gas after operating the turbine 2 through a duct 10 and thewaste heat boiler 4 is connected to the condenser 6 through a duct 11 tofeed the exhaust gas therein. The water-gas separator 7 is connected tothe condenser 6 to separate fluid from the condenser 6 into gascomponent mainly including the CO₂ and condensate. The water-gasseparator 7 is connected to the compressor 5 through a duct 12 and thecompressor 5 is also connected to the combustor 1 through a duct 16 andto the turbine 2 through a shaft 17. As described above, the powergeneration plant shown in FIG. 3 constitutes a closed cycle.

In this embodiment, a steam turbine 30 is further located in the powerplant and connected to the generator 3 through a driving shaft 9a. Thesteam turbine 30 is connected to a condenser 31 through a duct and thecondenser 31 is also connected to the waste heat boiler 4 through a duct32. A feed water pump 33 is incorporated on the way of the duct 32. Thewaste heat boiler 4 is connected to the steam turbine 30, whereby theturbine 30, the condenser 31 and the waste heat boiler 4 constitute aclosed cycle through the duct means and, accordingly, the powergeneration plant shown in FIG. 3 is called as a combined closed typepower generation plant.

According to the combined cycle power generation plant shown in FIG. 3,water condensed and stored in the condenser 31 is fed into the wasteheat boiler 4 by the actuation of the water feed pump 33 and the wateris superheated in the waste heat boiler 4 by the highly heated exhaustgas from the turbine 2 to generate superheated steam through the heatexchanging operation. The superheated steam is then fed to the steamturbine 30 to drive the same and in turn drive the generator 3 throughthe driving shaft 9a and the steam after utilizing the driving of thesteam turbine 30 is conveyed into the condenser 31 to condense the same.

With this embodiment, the condensate separated in the water-gasseparator 7 is removed therefrom by a suitable means W of known type andthe gas component mainly composed of the CO₂ is conveyed into the CO₂compressor 5 through the duct 12 provided on the way thereof with a CO₂gas removing means including the suction pump P and the reservoir R forremoving the excessive CO₂.

SO_(x) generated by the oxidation of sulfur which may be contained inthe fuel will be preferably removed by incorporating an SO_(x) removingmeans, for example a known wet washing type in the line 11 connectingthe waste heat boiler 4 and the condenser 6. As described above,according to the thermal power plant shown in FIG. 3, so called a closedcombined cycle gas turbine power generating plant, of this embodiment,the fuel gas is burnt in the combustor in the presence of the oxygen,instead of the air generally including nitrogen, oxygen or othercomponents, so that substantially no NO_(x) is contained in the exhaustgas and CO₂ is recycled as the main working gas and an excessive CO₂ isrecovered without emitting into atmosphere. The highly heated exhaustgas is utilized for the heat exchanging operation in the waste heatboiler 4 for producing the superheated steam for operating the steamturbine 30 which is operatively connected to the generator 3.

Accordingly, the environmental pollution can be substantially eliminatedwithout being equipped with specific means for removing harmful gas suchas NO_(x), SO_(x) and CO₂.

In addition, according to this embodiment, different from a conventionalopen type power generation plant, the water component in the exhaust gasis condensed, so that the discharge gas pressure can be reduced belowthe atmospheric pressure and, accordingly, the expansion ratio of theturbine can be made large, which results in the increasing of theturbine power generation efficiency.

FIG. 4 shows a block diagram representing the fourth embodimentaccording to this invention and a turbine power generation plant of thisinvention may be called a closed H₂ O gas fluid power generation systemfor the character described hereunder and, in FIG. 4, like referencenumerals are added to elements or units corresponding to those shown inFIG. 1.

With this embodiment, in principle, the line connecting the water-gasseparator 7 and the combustor 1 through the compressor for compressingthe CO₂ is eliminated in comparison with the embodiment shown in FIG. 1.In this meaning, this embodiment may be regarded as a generic embodimentaccording to this invention.

Namely, the fuel such as coal gas supplied from the fuel supply means Finto the combustor 1 is burnt therein in the presence of the oxygensupplied from the oxygen supply means O. The combustion gas from thecombustor 1 is delivered to the turbine 2 to drive the same and, hence,the generator 3 through the shaft 9. The exhaust gas from the turbine 2is fed into the waste heat boiler 4 through a duct 10, in which the heatexchanging operation is carried out between the exhaust gas and thecondensate from the condenser 6. The exhaust gas from the condensatewaste heat boiler 4 mainly including H₂ O and CO₂ is delivered into thecondenser 6, in which the water component of the exhaust gas iscondensed into condensate. The condensate is separated by the water-gasseparator 7 from the gas component mainly including the CO₂. Thecondensate is then delivered to the waste heat boiler 4 through the pumpmeans 14 and the CO₂ generated by the combustion of the fuel isrecovered into a CO₂ removing means including the suction pump P andreservoir R installed external to the power generation plant. Thecondensate in the waste heat boiler 4 is heated into superheated steamwhich is then fed into the combustor 1 as the working fluid for theturbine.

According to this embodiment, the water component in the exhaust gas isreused effectively as condensate without being discharged exterally tothe power generation plant and the superheated steam is utilized as themain working fluid for the turbine instead of the air as is in theconventional plant. Moreover, regarding the exhaust of the harmful gassuch as NO_(x), SO_(x) and CO₂, substantially the same advantages can beattained as those described in the forgoing embodiments.

In this embodiment, the fuel supply means F and the oxygen supply means0 may be connected to the waste heat boiler 4 so as to assist the heatexchanging operation performed therein.

According to these embodiments of the present invention, CO₂ included inthe exhaust gas can be recovered by cooling the exhaust gas after theutilization for the power generation without using any solvent forabsorbing the CO₂. The fuel is burnt in the combustor in the presence ofoxygen, not air, thermal NO_(x) which is caused by the oxidation of N₂included in the air is not formed. Any hydrocarbonic fuel such asliquefied natural gas and fuel oil may be utilized as a fuel as well ascoal gas, natural gas or petroleum gas, so that a thermal powergeneration plant will be realized in view point of long usage of energysource regardless of any variable factor for the fuel. In the embodimentin which H₂ O gas is utilized as a working fluid, the temperature of theworking fluid can be made high in comparison with a steam turbine powergeneration plant, so that the power generation with high efficiency canbe performed. In the embodiment in which the recovered CO₂ is utilizedas a working fluid, the water vapor component in the exhaust gas iscondensed by cooling the same, so that the discharge pressure from theturbine is made below the atmospheric pressure, different from aconventional gas turbine power generation plant, the power generationefficiency can be made remarkably high.

The thermal power generation plant according to this invention can berealized in combination of the exsisting plant. A known type oxygenproducing system can be utilized for the oxygen supply means which isconnected to the combustor and a known type CO₂ removing means can beincorporated in the plant.

It is to be understood by persons in the art that this invention is notlimited to the described embodiment and many changes and modificationsmay be made according to this invention without departing from the scopeof the appended claims.

What is claimed is:
 1. A thermal power generation plant of a closedcombined cycle structure comprising:a combustor in which a fuel is burntin the presence of an oxygen; a fuel supply means connected to saidcombustor to supply a fuel therein; an oxygen supply means connected tosaid combustor to supply an oxygen therein; a turbine operativelyconnected to said combustor to be driven by combustion gas from saidcombustor; a generator operatively connected to said turbine; a wasteheat boiler connected to said turbine which exhausts turbine exhaust gasmainly composed of carbon dioxide and water component; a condenserconnected to said waste heat boiler through a line for condensing thewater component in a cooled exhaust gas from said waste heat boiler, asulfur oxide removing means being incorporated in the line connectingsaid waste heat boiler and said condenser; a water-gas separatorconnected to said condenser for separating condensate and gas componentmainly composed of carbon dioxide, said water-gas separator beingconnected to said waste heat boiler to feed the condensate thereto; acompressor connected to said water-gas separator through a line forreceiving said gas component mainly composed of the carbon dioxide andfor compressing said gas component and supplying it directly to saidcombustor; a steam turbine connected to said waste heat boiler andconnected to said generator through a driving shaft; and a condensorconnected to said steam turbine and said waste heat boiler through aline through which said stream turbine, said condenser and said wasteheat boiler constitute a closed cycle.
 2. A power generation plantaccording to claim 1, wherein an excessive carbon dioxide removing meansis incorporated in a line connecting said water-gas separator and saidcompressor.
 3. A power generation plant according to claim 1, wherein acondensate recovery means is connected to said water-gas separator.